Place the first 7 ingredients in a 6-qt. electric pressure cooker; add chicken. Lock lid; close pressure-release valve. Adjust to pressure-cook on high for 7 minutes. Quick-release pressure. A thermometer inserted in chicken should read at least 165°., Remove chicken; cool slightly. Reserve 2 cups cooking juices; discard remaining juices. Shred chicken with 2 forks. Combine with reserved juices. Serve on buns with cheese and pickles.